This invention relates to battery charging devices, and in particular to a self-contained emergency battery charger for use in motor vehicles for charging a fully or partially discharged starter storage battery which delivers current to a starter motor of the vehicle.
A motor vehicle storage battery frequently falls into a state of discharge such that it cannot deliver sufficient current to the starter motor. This is often due to lights or other accessories being accidently left on. Also, defective vehicle charging systems can result in the same problem.
To start a vehicle whose storage battery has been partially or completely discharged requires either by-passing the electrical starting system entirely or supplying the electrical starting system with an additional source of external electrical power. The former technique is generally accomplished by push-starting the vehicle and the latter technique by using jumper cables connected to a fully charged external power source in another vehicle, termed "jump starting", or a conventional battery charger. Push starting requires assistance in the form of a push vehicle or human muscle power. Additionally, only cars fitted with standard transmissions can be push started. Jump starting requires the aid of an additional vehicle. Further, cables must be available and must be externally connected, requiring the user to exit the vehicle, and be exposed to the hazards of weather or of possible battery explosion and associated mishaps as a result of a misconnection of the cables. The disadvantage of a conventional battery charger is the need to be near a source of external power such as 120 volts alternating current.
To overcome these problems several self-contained emergency battery charges have been developed. These include U.S. Pat. Nos. 5,352,966 (Irons); 4,857,820 (Tompkins et al.); 4,004,208 (Tamminen); and 4,540,929 (Binkley). Irons' device provides a primary rechargeable battery source in conjunction with a secondary non-rechargeable battery source. The Irons' device is useful only for one or two battery charges before the secondary battery source must be replaced. The Tompkins device uses a primary rechargeable battery source in conjunction with a transformer. Tamminen's configuration has a very slow recharge cycle. Binkley's device offers passive current regulation with a resistor and also has a very slow recharge cycle.
Other devices in the art include those disclosed in U.S. Pat. Nos. 3,504,262; 4,258,305; and 3,763,415. Their disadvantages are a need for an external source of power, insufficient portability or lengthy charging/recharging times.